This invention relates generally to measuring and testing by dispersed light spectroscopy with Raman type light scattering, and more particularly to Raman spectroscopy for the determination of carbon-halogen and fluorooorganic compounds.
Qualitative and quantitative analysis of fluoroorganic compounds is an important practical task. Fluoroorganic compounds are widely used in the pharmaceutical industry. About one-third of all newly patented drugs contain carbon-fluorine (Cxe2x80x94F) bonds. Examples of fluorine-containing drugs are the anticancer drug Fluoracil (C4H3FN2O2, 5-fluorouracil), antidepressant drug Prozac(copyright) (C17H18F3NO, fluoroxetine) and painkiller Dalmane (C21H23ClFN3O, flurazepam). Perflubron (C8F17Br, bromoperfluorooctane) is an oxygen-carrier in a formulation now undergoing clinical trials as a blood substitute. Many agricultural chemicals and pesticides also contain carbon-fluorine bonds.
Chemical analysis for drugs can be done by isolating the drug and then measuring concentrations of compounds. This approach can be expensive. Alternatively, known chemical compounds can be labeled with radioactive elements to form tracers. The radioactive compounds and their metabolites can be followed in the body or tissues by observing emitted radioactivity. However, making and disposing of radiolabeled compounds is also expensive. These expenses can be found in many drug development programs.
Accordingly, the inventors have determined that it would be useful to accurately and inexpensively identify fluoroorganic compounds. The present invention provides a method and apparatus for achieving this object.
The invention is directed to an apparatus and method for detecting the presence of compounds having carbon-halogen bonds using Raman spectroscopy. The method detects any carbon-halogen bond, and is particularly useful in detecting carbon-fluorine bonds.
In one aspect, the method uses pulsed laser Raman spectroscopy to detect carbon-halogen bonds, using an effect of inelastic scattering of light. A sample is irradiated from a noncontinuous periodic pulse light source, such as a metal-vapor laser. Raman scattered light emitted from the sample is then detected to determine if a characteristic Raman scattered light spectrum for a compound having a carbon-halogen is present in the sample.
In another aspect, the apparatus for Raman spectroscopy includes a noncontinuous periodic pulse metal vapor laser and a monochromator for visible and ultraviolet light. The apparatus also includes a detector for detecting the emitted Raman scattered light and a pulse recording system to eliminate primary fluorescence associated with the sample.
In yet another aspect, the invention is directed to a method for detecting a fluoroorganic compound that includes exposing a sample to an excitation light source and measuring a frequency of an acoustic mode of the compound. The method also includes measuring a frequency of an optical mode of the compound and detecting a shift in the optical and acoustic mode frequencies. The molecular length of the compound is approximated as a function of the shift in frequencies to determine the presence of the fluoroorganic compound.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.